Cracking asphaltic materials



CRACKING ASPHALTIC MATERIALS James A. Dinwiddie, Max A. Mosesman, and Charles L.

Thorpe, Baytown, Tex., assignors, by mesne assignments, to Esso Research and Engineering Company, Elizabeth, N..l'., a corporation of Delaware Application February 28, 1955, Serial No. 490,788

Claims. (Cl. 208-411) The present invention is directed to an improved process for producing valuable products from asphaltic materials. It particularly relates to an improved process for hydrocracking asphaltic substances employing a solid porous catalyst containing supported thereon oxygencontaining compounds of molybdenum, cobalt and either nickel or iron.

Briefly, the process of the present invention may be described as contacting an asphalt-containing substance such as asphalt, a diluted asphalt, a residuum derived from a petroleum crude oil and the like with a hydrocracking-desulfurization catalyst comprising a porous support containing catalyzing amounts of oxygen compounds of molybdenum and cobalt and in addition oxygen compounds of a metal selected from the group consisting of nickel, iron and mixtures thereof. The support used is preferably an alumina. The hydrocracking-desulfurization is preferably carried out in the presence of hydrogen at pressures below about 1000 p.s.i.g.

The asphaltic material may be derived from a variety of sources such as crude petroleum oils, hydrogenated coals, bitumens, coal tar fractions and other sources of natural and synthetic origin, and will have characteristics well known to those skilled in the art. For example, it may be obtained by deasphalting a residue resulting from the distillation of crude petroleums such as the residual fractions obtained by distillation of Panhandle crude and the like. The invention has particular application to conversion of asphaltic materials derived from crude petroleum oils. Although an essentially asphaltic material may be used in the practice of the present inven tion, it is preferred that it be diluted with a suitable lower boiling diluent. For example, a crude oil residue such as one representing the lower to 25% fraction of the crude oil, and comprising hydrocarbons boiling in the gas oil and/or lubricating oil boiling range may be used. In other cases it may be desired to blend an essentially asphaltic material with a suitable diluent such as a gas oil or lower boiling hydrocarbon boiling in the range of about 200 to 1000 F., but preferably boiling from about 430 to 650 F. Such diluted asphalts are preferred because they are more easily handled than the viscous semi-solid asphalts themselves and also since they have less tendency to contaminate catalytic materials during the hydrocracking operation.

In a suitable form of the invention, the asphaltic material is passed through a fixed bed of granular catalyst in the presence of a hydrogen containing gas at elevated temperatures and pressures. Temperatures may suitably range from about 700 to 1000 F., but preferably range from about 750 to 800 F. Relatively low pressures may be used in contrast to conventional asphalt hydrogenation processes, those in the range of about 100 to 1000 p.s.i.g., preferably from about 300 to 600 p.s.i.g. are useful.

Space velocities in the reaction zone may range from about 0.1 to 5 volumes of feed per volume of catalyst per hour (v./v./hr.) with those in the range from 0.25 to such as by wet mulling the base and the mixture of oxides 2,882,221 Patented Apr. 14, 1959 2 v./v./hr. being especially useful. The hydrogen may be any suitable hydrogen-containing material which may be employed in an amount in the range from about 500 to 6000 cubic feet of hydrogen per barrel of feed mixture, a preferred amount being in the range of 500 to 2000 cubic feet per barrel.

Various supports may be used in preparing catalysts of the present invention including such materials as alumina, silica gel, activated carbon, mixtures of silica and alumina and the like; however, alumina is greatly preferred when the desulfurizing activity of the catalyst is to be emphasized. On the other hand, predominantly siliceous bases may be preferred when cracking intensity is to be increased during the asphalt treating operation.

The concentration of the metals, calculated as the oxides, on the support may vary from about 3 to 30%, based on the total weight of the catalyst, but preferably the total concentration will range from about 10 to 25 weight percent. The catalyst may contain oxides of both molybdenum and cobalt, either in the form of individual oxides or as complexes or compounds such as cobalt molybdate. The ratio of molybdenum to cobalt, calculated as the oxides, may vary from about 5:1 to 1:5. However, ratios of molybdena to cobalt oxide of from 2:1 to 1:2 will 'be preferred as a general rule in producing catalysts having high desulfurization activity and improved hydrocracking characteristics. The amount of molybdenum, calculated as the oxide, on the total catalyst may vary over a rather wide range such as from about 5 to 20 weight percent in the preferred embodiments of this invention with cobalt oxide contents ranging from about 1 to 10% by weight.

The amount of nickel and/or iron oxides employed will usually be less than the amount of molybdena used, with concentrations ranging from as low as 0.5 up to as high as 10 weight percent. Nickel oxide is a preferred auxiliary promoter to be used with the molybdena and cobalt oxide when it is desired to obtain relatively high desulfurization and hydrocracking activity throughout a wide range of asphalt treating temperatures. On the other hand, iron oxides will be a preferred auxiliary promoter when it is desired to emphasize desulfurization of the asphalt but to reduce hydrocracking tendencies. Other types of metals and metal-containing materials may be used on the catalyst in conjunction with the above mentioned catalytic agents.

In a preferred embodiment of the present invention, the finished catalyst composition is characterized by having a relatively high most frequent pore diameter (D in A. and a relatively wide spread in the range of the more frequent pore diameters in A. (AD Desirable methods for determining these physical characteristics of catalytic compositions, and for preparing compositions having such characteristics are described in detail in copending US. application Ser. No. 490,732, filed on even date herewith in the names of James A. Dinwiddie, Max A. Mosesman, James A. Anderson, Jr. and Lonnie W. Vernon and entitled Improved Porous Contacting Agents and Use Thereof. Specifically, the catalyst of the present invention preferably has D, values above 50 A. and preferably in the range of about to 400 A. with AD values ranging from about 10 to A. As described in the aforementioned Dinwiddie et al. application, such materials have high pore size distribution factors in the range of about 10 to 300, and are much to be preferred in contacting mixtures of molecules having large molecular diameters such as are found in asphaltic materials and the like. i e

The various metal oxides used in accordance with the present invention may be impregnated in or supported on the porous base material by a number of procedures or salts of the metals that may be converted to the oxides by heating, or mixtures of oxides and salts that form the desirable composition in the final stages of preparation. The wet mulled mixture may then be dried, heated or calcined at elevated temperatures and pilled or screened into the form of catalyst granules having the desired particle size.

A preferred procedure comprises forming a porous base having impregnated thereon cobalt and molybdenum in the desired amount and ratio, and in the form of oxides or complexes, this base having been formed by conventional procedures, dried, and preferably heat treated at temperatures as high as 1000 to 1200 F. This base is then wet mulled with a decomposable salt of nickel or iron, such as the nitrate or acetate, following which it is dried and preferably activated by heating to elevated temperatures such as 800 to 1300" F. or higher. Prior to contact with the asphaltic feed, the catalyst may suitably be contacted at an elevated temperature with a portion of sulfur containing diluent oil.

The present invention may be further illustrated by reference to the drawing in which the single figure is a flow diagram of a preferred mode of operation.

Referring now to the drawing, numeral 11 designates a tank in which a feed mixture of asphaltic material may be accumulated. The feed mixture may be formed by introducingan asphaltic hydrocarbon, which may be a crude residue, by way of line 12 containing pump 13 and controlled by valve 14 into tank 11 by way of line 15 in admixture with a diluent hydrocarbon from a source not shown which is introduced into the system by way of line 16 containing pump 17; line 16 is controlled by valve 18. Line 16 connects into line 15 which, in turn, is controlled by valve 19.

The feed mixture in tank 11 is withdrawn therefrom by line 20 controlled by valve 21 and is pumped by pump 22 into a reaction zone 23 which suitably contains a bed 24 of a catalyst of the nature described which, for purposes of this description, may be cobalt molybdate and nickel oxide on alumina. On passing through line 20 there is added to the feed mixture by way of line 25 controlled by valve 26 a su'flicient amount of hydrogen in the range given to allow the reaction to proceed as is desired. The feed mixture including hydrogen added by line 25 is heated to reaction temperatures by passage through a furnace 7 containing a heating coil 8 which is supplied with heat from burners 9. The heated mixture discharges from coil 8 by line 20a into reaction zone 24.

On passage of the mixture of hydrogen and feed through the reaction zone 24, the asphaltic hydrocarbons are substantially converted in a cracking reaction to bydrocarbons of lower boiling range; such hydrocarbons produced in the process may" include naphtha, heating oil and heavier hydrocarbons. Some desulfurization of the asphalt may take place. The converted product discharges from reaction zone 23 by line 27 which leads into a separation zone 28 wherein a separation is made between the fixed gases containing unconsumed hydrogen and the converted product. The hydrogen and other fixed gases are Withdrawn from zone 28 by line 29 and may be recycled to line 25 while the converted products issue from zone 28 by line 30 and discharge thereby into a distillation zone 31 which may be a single distillation tower or a plurality of fractional distillation towers. Distillation zone 31, while shown diagrammatically in the drawing, is intended to include all auxiliary equipment usually associated with the modern distillation tower. For example, the zone 31 will include cooling and condensing means, means for inducing reflux and internal vapor-liquid contact means, such as bell cap trays, packing and the like. Zone 31 is also provided with a heating means illustrated by a steam coil or equivalent heating means 32 for adjustments of temperature and pressure. Zone 31 is also provided with line 33 'for removal of fractions lighter than gasoline, line 34 for removal of gasoline and naphtha hydrocarbons, line 35 for withdrawal of heating oil fractions and line 36 controlled by valve 37 for Withdrawal of catalytic cracking feed. Zone 31 is also provided with line 38 for discharging of heavier fractions.

Zone 31 may be operated in any number of different ways. For example, all of the light fractions may be taken off as one fraction including heating oil, gasoline and lighter materials, leaving the catalytic cracking feed and the heavier fractions to be withdrawn by line 38 with valve 37 being closed. If desired, the lighter components of the diluent fraction may be withdrawn by line 36 and the heavier fraction Withdrawn by line 38 subjected to suitable deasphalting and other treatments to recover cracking stock and the like diluent. Either of the several fractions may be recycled to line 16, such as the fractions withdrawn by lines 35, 36, and 38 as desired.

It is desirable in the practice of the present invention to charge the feed mixture to the reaction zone 23 until the conversion to desirable products tends to decrease. When such happens, valve 21 may be closed and valves 14 and 19 also closed allowing the diluent hydrocarbon to be routed by line 16 directly into line 20 and thence into the zone 23 over the catalyst bed 24 in admixture with hydrogen introduced by line 25 as desired. This operation allows the catalyst to be regenerated. The diluent feed is continued over the catalyst for a period of time ranging from 8 to 48 hours and thereafter the valve 19 is opened and valve 39 in line 16 is closed allowing the feed mixture on opening valve 21 in line 20 to be routed again to reaction zone 23. Of course, valve 14 in line 12 may be opened allowing the makeup of feed mixture in tank 11.

The present invention results in the production of useful products, such as naphthas, gasolines, heating oils and gas oils from asphaltic materials. The invention is dependent on a number of operating variables. For example, pressure is important since at low pressures, for example, below pounds per square inch gauge operating temperature must be kept low and the overall reaction rate tends to fall olf. The amount of diluent volatilized from the catalyst increases and with sutficient volatilization of the diluent coking of the catalyst takes place. Operating at higher pressures, but below 1000 pounds per square inch gauge allows the overall reaction toward desirable products to be increased since operating temperatures in the range given may be increased. In general, higher temperature results in increasing the ratio of gasoline to gas oil in the product. If pressures above 1000 pounds per square inch gauge are employed, gas production increases and hydrogen consumption increases which tends to make the process undesirable.

During the course of operation the catalyst will tend to lose its ability to convert the asphaltic material to desirable hydrocarbons. It may suitably be regenerated by cutting out the asphaltic component of the feed mixture and charging only the diluent to the catalyst bed in the presence of hydrogen at reaction conditions. The period of charging the diluents in the absence of asphalt may range from about 8 to 48 hours, sufiicient to recondition the catalyst for conversion of asphalts to desirable hydrocarbons. After repeated reconditioning of the catalyst with diluent hydrocarbon it may become necessary to subject the catalyst to more severe regenerating conditions such as for example treatment with an oxygen-containing gas to burn off coke-like deposits which were not removed by conditioning the catalyst with diluent hydrocarbon. The conventional procedures for oxidative regeneration may be used which will include the steps of displacing hydrocarbon from the catalyst zone such as by purging with an inert gas followed bycontrolled addition of oxygen-containing gas to the zone either alone or in admixture with inert gas such as flue gas.

The invention will now be described in more detail in connection with the following example.

API gravity and sulfur content. The increase in gravity of the product over the charge stock is a measure of the extent to which hydrocracking of the asphalt takes place.

The results of these runs are shown in the table:

Table Catalyst Used 1 2 3 4 Catt l yst Composition, Wt. Percent 9 8. 5 8. 5 8. 5 C00..- 3 2.9 2.9 7.9 Ni0 0 6 0 0 Ferosu 0 0 5.0 0 Wt. Ratio, M00;:CoO.-. 3:1 29:1 2. 9:1 1.08:1

Reaction Temp., F 750 775 800 750 775 800 750 775 800 750 775 800 Charge Product Inspections:

Gravity API l9. 5 22. 6 23.3 23. 8 24. 4 24.3 25.0 23. 4 23. 3 24. 4 23. l 22. 6 25.0 Sulfur, Wt. Percent 1. 76 0. 92 0. 91 0. 95 0. 71 0.72 0.65 0.75 0.78 0.72 0. 88 0.93 0. 61 Increase in Gravity of Product over charge, API 3. 1 3. 8 4. 3 4.9 4. 8 5. 5 3. 9 3.8 4.9 3. 6 3. 1 5. 5

1 All catalysts prepared with support containing 6 weight percent silica and 94 weight percent A110,.

EXAMPLE A series of hydrocracking operations were carried out employing the following catalysts:

Catalyst 1.-This catalyst was a conventional alumina base catalyst promoted with cobalt oxide and molybdena. The base contained about 94 weight percent alumina and 6 weight percent silica, and the final catalyst composition was about 3 weight percent C00, 9% M00 5% SiO; and 83% Al O The catalyst was pilled in the form of Va" x /s" pills and heat treated for four hours at about 1100 F. before use.

Catalyst 2.A portion of catalyst 1 was wet mulled with nickel nitrate, dried at 230 F. and activated for 24 hours at 1100 F. following which it was pilled into the form of A3" pills. Suflicient nickel nitrate was used in this preparation to form a finished composition containing 5 weight percent NiO.

Catalyst 3.-This catalyst was prepared in the same manner as catalyst 2 except that iron nitrate rather than nickel nitrate was used in the preparation. Sufiicient iron nitrate was employed to form a finished catalyst containing 5 Weight percent Fe O Catalyst 4.This catalyst was prepared by the same procedure used in preparing catalyst 2 except that sufficient cobalt nitrate was added thereto to form a finished catalyst composition containing an equivalent of about 7.9 weight percent of cobalt oxide.

The common feed stock employed in all of the hydrocracking runs was a blend of 60 weight percent Coastal light gas oil and 40 weight percent asphalt obtained by conventional solvent deasphalting of mixed residua obtained from crude petroleum oils. The Coastal gas oil had a gravity of 31.7 API, 21 5 to 95% ASTM boiling range of from 460 to 596 F., and contained 0.1 weight percent sulfur. The asphalt had a Furol viscosity at 325 F. of 915, a softening point of 205 F., and a specific gravity of 60/60 F. of 1.0752. The gas oil asphalt blend contained 1.76 weight percent sulfur and had an API gravity of 19.5.

All of the runs were carried out in a fixed bed reaction zone using a liquid space velocity of 0.5 v./v./hr., a reactor pressure of 400 p.s.i.g. and a hydrogen feed rate of 1000 cubic feet per barrel. In runs carried out with a given catalyst, the reactor was operated for 16 hours at a temperature of 750 F., the reactor temperature was increased to 775 F. and operated for another 16 hours, and then the reactor temperature was increased to 800" F. for another 16 hour period. The total products from each 16 hour period were withdrawn and evaluated for At all three temperature levels, catalysts 2 and 3 containing either nickel or iron oxide in addition to molybdena and cobalt oxide, gave improved desulfurization and increased hydrocracking over the base catalyst l. The nickel oxide-containing catalyst was somewhat more active in both categories than that containing iron oxide. On the other hand, when it is desired to maintain a rather high level of desulfurization with an intermediate level of hydrocracking, the iron oxide catalyst is to be preferred.

By decreasing the molybdena cobalt oxide ratio from 3:1 in catalyst 1 to about 1.121 in catalyst 4, the hydrocracking and desurfurization activity of the catalyst was improved particularly at high temperature levels such as 800 F. It is, therefore, preferable to use relatively high concentrations of both molybdena and cobalt oxide at substantially equal weight ratios when it is desired to form a base for the iron oxide and nickel oxide auxiliary supports having even greater activity than those shown in the case of catalysts 2 and 3.

What is claimed is:

l. A process for hydrocracking and desulfurizing an asphaltic material which comprises contacting the said asphaltic material with a fixed bed of catalyst in the presence of added hydrogen under conversion conditions including a temperature within the range of about 700 to 1000 F., a pressure within the range of to 1000 p.s.i.g., and a space velocity within the range of about 0.5 to 5 volumes of feed per volume of catalyst per hour, said catalyst consisting essentially of an alumina base having supported thereon oxygen-containing compounds of molybdenum and cobalt within the range of about 5 to 20 weight percent and in the range of about 0.5 to 10 weight percent, based on the total catalyst, of an oxide of a metal selected from the group consisting of nickel, iron and mixtures thereof.

2. A process as in claim 1 wherein the ratio of molybdenum to cobalt in said catalyst, calculated as the oxides thereof, is in the range of about 5:1 to 1:5 and the concentration of molybdenum on said catalyst, calculated as the oxide, is in the range of about 5 to 20 weight percent based on the total catalyst.

3. A process for the hydrocracking and desulfurization of asphaltic materials which comprises the steps of contacting the asphaltic material with a fixed bed of catalyst under conversion conditions including a temperature within the range of 750 to 800 F., a pressure within the range of 300 to 600 p.s.i.g. and a space velocity within the range of 0.25 to 2 volumes of feed per volume of catalyst per hour in the presence of added hydrogen, said catalyst consisting essentially of from about 5 to 20 weight percent of molybdena, from about 1 to 10 percent of cobalt oxide, from about 2 to 10 percent by weight of an oxide of a metal selected from the group consisting of nickel, iron and mixtures thereof, and the remainder of said catalyst consisting essentially of silica stabilized gamma alumina.

4. A method as in claim 3 wherein the ratio of molybdenum to cobalt in the catalyst, calculated as the oxides thereof, is in the range from about 5:1 to 1:5.

5. A method as in claim 4 wherein the said ratio of molybdenum to cobalt, calculated as the oxides thereof, is substantially 1:1.

iieferences Cited in the file of this patent UNITED STATES PATENTS 2,227,671 Pier et al.- Jan. 7, 1941 2,369,432 Byrns Feb. 13, 1945 2,638,454 Rowan May 12, 1953 2,690,433 Engel Sept. 28, 1954 2,717,855 Nicholson 1 Sept. 13, 1955 2,723,943 McAfee Nov. 15, 1955 2,739,132 Riedl 1 Mar. 20, 1956 2,768,936 Anderson et al. Oct. 30, 1956 2,801,208 Home et al. July 30, 1957 OTHER REFERENCES Sachanen: Conversion of Petroleum, 2nd edition 1948), pp. 374-377. 

1. A PROCESS FOR HYDROCRACKING AND DESULFURIZING AN ASPHALTIC MATERIAL WHICH COMPRISES CONTACTING THE SAID ASPHALTIC MATERIAL WITH A FIXED BED OF CATALYST IN THE PRESENCE OF ADDED HYDROGEN UNDER CONVERSION CONDITIONS INCLUDING A TEMPERATURE WITHIN THE RANGE OF ABOUT 700* TO 1000* F., A PRESSURE WITHIN THE RANGE OF 100 TO 1000 P.S.I.G., AND A SPACE VELOCITY WITHIN THE RANGE OF ABOUT 0.5 TO 5 VOLUMES OF FEED PER VOLUME OF CATALYST PER HOUR, SAID CATALYST CONSISTING ESSENTIALLY OF AN ALUMINA BASE HAVING SUPPORTED THEREON OXYGEN-CONTAINING COMPOUNDS OF MOLYBDENUM AND COBALT WITHIN THE RANGE OF ABOUT 5 TO 20 WEIGHT PERCENT AND IN THE RANGE OF ABOUT 0.5 TO 10 WEIGHT, BASED ON THE TOTAL CATALYST, OF AN OXIDE OF A METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL, IRON AND MIXTURES THEREOF. 